The present invention relates generally to a transient power supply and, more particularly, to method and apparatus for providing transient power by converting stored kinetic energy into electrical energy.
Typically, electrical devices receive operating power from an external power distribution grid that is coupled to a power generation facility, such as a power plant, for example. From time to time, this external power source can be interrupted, because of a malfunction in the generation facility and/or in the distribution grid, for instance. Accordingly, certain electrical devices are connected to an auxiliary power source, such as a diesel generator or a bank of batteries. Unfortunately, transitioning from the external power supply to the auxiliary power supply is generally not instantaneous and, as such, presents an interval of time during which the electrical devices are without power. For certain critical devices, such as computers or medical devices, even a momentary loss of power can lead to undesirable effects, such as a loss of critical data and/or malfunction of the device.
Accordingly, these critical devices traditionally have been coupled to a transient power supply, which is often referred to as an uninterruptible power supply (UPS) by those of ordinary skill of art in the industry. In summary, a transient power supply (i.e., UPS) provides operating power to the critical device from when the primary power is lost to the time at which the auxiliary power is brought on-line. Traditionally, battery banks have been employed to provide this transient power. As another example, certain flywheel devices have been employed to provide transient power.
Traditional flywheel devices include a rotating flywheel that is coupled to a generator and a motor. During normal operation, the motor operates off of main or primary power and energizes (i.e., kinetic energy of rotation) the flywheel. However, when power is lost, the flywheel remains in motion and operates a traditional generator, which generates power by rotating a permanent magnet or electromagnet within a stator core to induce current within stator windings disposed around the permanent magnet or electromagnet.
Unfortunately, traditional transient or UPS power sources are not without drawbacks. For example, battery banks that provide sufficient levels of power can be relatively expensive to purchase and maintain and, furthermore, often consume relatively large areas of floor space. In an industrial setting, for instance, cost and floor space are relevant concerns. As another example, traditional flywheel devices often require the maintenance of high rotation rates to generate sufficient and appropriate power. Accordingly, traditional flywheel devices often employ vacuum chambers to reduce the dissipation of kinetic energy from the flywheel due to air resistance, for example. Additionally, traditional flywheel devices employ a motor to energize the flywheel and a separate permanent magnet generator to convert the kinetic energy of the flywheel in to electrical power. By using two distinct devices (i.e., the generator and the motor), traditional systems bear a greater cost, and the use of the permanent magnet also increases the cost of the system. Furthermore, maintaining a vacuum condition for the flywheel increases the cost and likelihood of failure for the system.
Therefore, there exists a need for improved methods and apparatus for providing a transient power supply to certain electrical devices.